I understand your frustration, but you will be able to select “two preferred seating areas”, and you won’t be obliged to accept anything outside of these areas if either of those are not available, so you’d know that the extra seat wouldn’t be THAT far away from your STs. Be interesting to see how specific the “seating area” requests will be, eg a specific block number would be much better than a specific stand etc.
Also couldn’t one of the adult STHs sit in the additional seat, and then your young lad sit next to the rest of the group?
Appreciate you would specifically want the seat next to your STs for your son, but even under the previous system of first come first served and choosing your own seat, the likely hood of being able to choose that specific one would be extremely slim. You’d be up against 1000s of others all trying to choose and grab a seat at the same time, so by the time you’d got through the Virtual Queue and got onto the website to buy, there’d be a good chance that specific seat had already been snapped up.